Electromagnetic relay with a suspended armature



Feb, 3, 1970 H. E. ASHWORTH ETAL 3,493,903

ELECTROMAGNETIC RELAY WITH A SUSPENDED ARMATURE Filed Aug. 5; 1968 2 Sheets-Sheet 1 fns ulargarz [NI [A7 03 1/01 E! Him "(h and 1 71; ArmBAz'f 1970 H. E. ASHWORTH ETAL 3,493,903

ELECTROMAGNETIQ RELAY WITH A SUSPENDED ARMATURE "2 Sheets-Sheet 2 Filed Aug. 5, 1968 United States Patent Office 3,493,903 Patented Feb. 3, 1970 3,493,903 ELECTROMAGNETIC RELAY WITH A SUSPENDED ARMATURE Harry E. Ashworth, Penn Hills, and Walter F. Kosar, Forest Hills, Pa., assignors to Westinghouse Air Bral e "Company, Swissvale, Pa., a corporation of Pennsylvania Filed Aug. 5, 1968, Ser. No. 750,147 Int. Cl. H01h 67/02 US. Cl. 335135 17 Claims ABSTRACT OF THE DISCLOSURE An electromagnetic relay comprising an electromagnetic structure, a molded contact pile-up and a molded armature assembly. The molded contact pile-up is supported by the electromagnetic structure and includes a plurality of elongated stationary and movable contact springs. The molded armature assembly includes a driver which is fixed to the free ends of the elongated movable contact springs so that the armature is suspended in relation to the electromagnetic structure. A stop member which is integrally formed with the molded armature assembly establishes a magnetic air gap between the armature and the electromagnetic structure.

Our invention relates to an improved electromagnetic relay and more particularly to a multiple contact type of relay including a suspended armature assembly and adapted for either plug-in or hand-wired installations.

Generally, relays adapted for use in communication applications, such as telephone and signaling systems, comprise an electromagnet in the form of a magnetizable core and an energizable coil, a movable armature operated in response to the energization and deenergization of the coil, and a plurality of stacked contacts including movable contacts which cooperate. with stationary contacts to interrupt or establish various electrical circuits in response to operation of the movable armature.

In such relays, it is customary to provide an armature member which is pivotally suported in relation to the magnetizable core and is attracted toward the core when the coil is energized and is biased away from the core when the coil is deenergized. This armature movement is usually translated to the movable contacts through suitably insulated operating members or lift pins for causing the required circuit making and/ or breaking action.

While these previous types of relays have been generally acceptable in regard to past needs, the present competitive market has stimulated and renewed activities for improving the operation of the relay as well as for reducing its overall manufacturing cost. It has been found that electromagnetic relays having pivotally mounted armatures are susceptible to such deleterious effects as mechanical binding as Well as excessive frictional weal which not only shortens the useful life of the relay but also requires frequent attention and constant repair. Further, relatively oversize coils are necessary for handling and overcoming the additional losses due to frictional drag and spring biasing. Therefore, it will be appreciated that the problems of binding and mechanical resistance have been found to be the most common cause of trouble in such relays. In addition to these, other perplexing problems, such as, undue complexity, excessive insulative requirements, adverse vibration and shock effects, extreme contact bounce and the overall number of parts required in prior art types of communication relays have resulted in a highly complicated electromechanical device which is economically expensive to produce as well as to maintain.

Accordingly, it is an object of our invention to provide a new and improved electromagnetic relay for solving the above-mentioned problems.

Another object of our invention is to provide an electromagnetic relay having a suspended armature assembly which is not susceptible to frictional wear and is gravity biased toward its released position.

A further object of our invention is to provide an improved multiple contact type of relay which requires a minimum number of parts thereby reducing the cost of manufacturing and maintenance.

Yet a further object of our invention is to provide an improved suspended armature relay in which the contact ture assembly comprising an armature member, a stop member and a movable ladder for operating a plurality of electrical contacts.

Yet another object of our invention is to provide an iprovedsuspended armature relay in which the contact assembly comprises a plurality of molded contact stacks which may be readily assembled and replaced with very little effort and within a minimum amount of time.

Still another object of our invention is to provide a new and improved relay having an electromagnetic structure supporting a contact assembly comprising a plurality of elongated heel contact springs, the free ends of which carry and guide a movable molded assembly comprising an operating ladder, an armature and a stop member which dampens and substantially elminates armature vibration and minimizes contact bounce.

"Still a further object of our invention is to provide a suspended armature relay which is adapted for either standard plug-in or soldered connections so that it is compatible with either new or existing installations.

"Still yet a further object of our invention is to provide a new and improved electromagnetic relay which is simple in construction, economical in cost and efiicient and reliable in operation.

Further objects, features and advantages of our invention will become more apparent as the following description proceeds and the ingenuity and novelty which characterizes our invention will be pointed out particularly in the claims appended which form part of our specification.

Generally, our invention relates to an electromagnetic relay comprising an electromagnetic assembly, a molded contact assembly and a molded armature assembly. The electromagnetic assembly includes an energizable coil, a core and a pair of pole pieces. The core extends through the center of the coil while pole pieces are disposed at either end of the coil in engagement with the core. Each pole piece includes a portion extending laterally from the core to one side of the coil and includes a portion extending parallel to the longitudinal axis of the coil. The molded contact assembly includes a plurality of contact sets each having a plurality of elongated stationary and movable contact springs all molded in superimposed relation in a block of insulating material. A fixed ladder is disposed adjacent the free ends of the contact springs for holding the elongated stationary contacts in their normal rest positions. A stack plate has an intermediate portion engaging the blocks of insulating material and has a forward extending portion engaging the fixed ladder for holding the blocks and fixed ladder to parallel extending portion of one of the pole pieces. The molded armature as sembly includes an operating ladder, an armature member and a stop member. The operating ladder is suspended from the free ends of the elongated movable contacts so that the armature member is disposed below and is attracted upwardly toward the undersurface of the parallel extending portions of the pole pieces when the coil is energized, and the stop member is disposed above and rests upon the upper surface of the parallel extending portions of the pole pieces when the coil is deenergized.

A better understanding of our invention will be had by reference to the drawings in which like reference characters refer to similar parts throughout the several views and in which:

FIG. 1 is a side elevational view of the electromagnetic relay embodying the present invention with a portion of the contact assembly broken away.

FIG. 2 is a cut-away perspective view of the movable armature assembly employed in the relay of FIG. 1.

FIG. 3 is a top view of the relay of FIG. 1 with portions broken away.

FIG. 4 is a front elevational view of the relay of FIG. 1 with a portion of one of the electromagnetic pole pieces broken away for showing various details of the armature assembly.

FIG. 5 is a rear elevational view of the relay of FIG. 1.

Referring now to the drawings and more particularly to FIG. 1, it will be noted that the electromagnetic relay generally characterized by numeral I basically includes an electromagnetic assembly 2, a multiple type of molded contact assemly 3, and a molded movable armature assembly 4.

As shown, the electromagnetic assembly 2 includes an energizable coil or winding 8 which is carried by a suitable insulating spool 9 having a circular end flange 9a and a square-edged end flange 9b. A cylindrical magnetic core 10 extends through the center of spool 9 and has its rear end securely fastened, such as by welding, to the laterally extending portion or leg of a first L-shaped pole piece member 12 which is preferably of rectangular cross section. As shown, a spring washer 14 encircles the core member 10 and is disposed between the pole piece member 12 and the flange portion 9a of the insulative spool 9. The spring washer 14 reduces the tolerance requirements of the various parts and also prevents undue compressive forces to be exerted on the insulative spool and coil yet provides a tight fit by taking up what end play remains after assembly. Preferably, the front end of the core 10 has a reduced threaded portion which is adapted to pass through a suitable circular opening in a laterally extending portion or leg of a second L-shaped pole piece member 13 which is also of rectangular cross section. As shown in FIGS. 1, 3 and 4, a relay handle member 16 is disposed adjacent the pole piece 13 and also encircles the threaded portions of the reduced core portion. The handle 16 is provided with a diagonally extending hand gripping portion 16a, and an inwardly extending flange portion or tab 16b, the purpose of which will be described presently. A cap nut 17 is screwed onto the threaded portion of the core for retaining the handle 16 and the L- shaped pole piece 13 in place and for urging the flange 9a of the spool 9 against the spring washer 14 thereby firmly holding the parts together. As shown in dotted lines in FIG. 4, the square edge of flange portion 9b cooperates with upper flat surface of the inwardly extending tab 16b for preventing rotational movement of the coil and spool. While the laterally extending legs of each of the L-shaped pole pieces are rigidly secured to the respective ends of the core 10 and extend in the same direction, the other legs of the L-shaped pole pieces extend parallel to the longitudinal axis of the core 10. These horizontal extending legs of the pole pieces 12 and 13 extend toward each other to within a short distance of each other for defining a suitable magnetic air gap 18.

As shown, the horizontal extending leg or portion of pole piece member 12 is employed for supporting the remaining structure of the relay proper. For example, the molded contact assembly 3 includes a plurality of contact sets or stacks each comprising a molded block of I suitable insulating material and a plurality of fixed and movable spring contacts which are disposed in superimposed cooperative association with each other. While three contact sets have been illustrated for the sake of convenience, it will be understood that a greater or lesser number of sets may be employed in practicing the present invention. Each of the contact sets is shown including a block of suitable insulating material 19 in which are molded two combinations of dependent stationary or fixed and movable contact springs 22, 23 and 24, respectively. Further, it will also be understood that various combinations of dependent and/ or independent contact sets may be equally used in practicing the present invention. The insulating blocks 19 are suitably disposed in side-by-side relationship on the upper surface of the horizontal leg of the pole piece 12. It will be noted that each side of the blocks is provided with a semi-circular groove or cylindrical recess 20 extending the length thereof, the purpose of which will be described hereinafter.

In order to facilitate positioning of the insulating blocks in side-by-side relationship, it is preferable to provide a cylindrical projection on the bottom of each of the insulative blocks 19, one of which is shown at 19a in FIG. 1. As shown, the projections are adapted to fit snugly into suitable holes provided in the horizontal leg of the pole piece member 12. Further, it will be noted that each block 19 is also provided with suitable notches 21 on each of the upper respective corners thereof, the purpose of which will be described later. As shown, the stationary and movable contact springs are provided with rearwardly extending terminal portions 22a, 23a and 24a, respectively, which are adapted for electrical attachment to the various external circuits. The relay may be hand wired to the external circuits, such as, by soldering the ends of the lead wires to the apertures, shown in FIG. 3 provided in the respective terminal portions. Alternatively, the relay must be employed for plug-in installation with a suitable mounting base, as will be described hereinafter. It will be noted that the forward extending portions of the fixed contact springs 22 and 23, namely, the front and back contacts are preferably bifurcated and that each bifurcation is provided with a separate contact point or tip 22b and 23b, respectively. It will be appreciated that with the free ends having separate or dual contact points the electrical contact characteristics are improved. A dual heel contact point or tip 24b is also provided on each of the movable contact springs 24 for cooperative association with the respective contact tips of the front and back contacts. It will be noted that the movable contact springs are formed with an offset portion 25 and a punched tab portion 26 at their free ends, the purpose of which will be described in greater detail hereinafter.

As shown, the horizontal extending leg of the L-shaped pole piece member 12 also carries a fixed ladder 30 which maintains the fixed or stationary contact springs in their normal rest position. The fixed ladder 30 is preferably constructed of a suitable insulating material, such as clear polycarbonate, and includes a plurality of laterally extending projecting shoulders or cross pieces 31 which cooperate with the various contact springs. The fixed ladder 30 is provided with a circular projection 32a on the top surface thereof, the purpose of which will be described hereinafter. The fixed ladder 30 is also provided with a pair of circular projections 32b on the bottom thereof, one of which is illustrated in FIG. 1, which are adapted to fit in suitable holes in the longitudinal leg of the L-shaped pole piece member 12. Further, as shown in FIG. 4, the fixed ladder 30 includes a rectangular opening 33 through which the elongated contact springs can pass for actuation purposes.

In the presently described arrangement, the fixed ladder and particularly the projecting shoulders or cross pieces 31 cooperate with contact springs to permit an open transfer function, namely, a break-before-make switching operation of the contacts. However, it is read- 1ly understood that the projecting shoulder or cross pieces 31 of the fixed ladder may be arranged to provide an overlap transfer function, namely, to make-before-break switching operation.

The contact assembly also includes a stack plate 34 having a forward extending portion 35 and a rearward extending portion 36. The intermediate portion of the stack plate 34 is provided with a pair of downwardly projecting tabs 37 on each side thereof which coope atively engage the two outer corner notches 21 of each of the outer insulating blocks 19. It will be noted that the forward extending portion 35 includes a suitable hole 35a for accommodating the cylindrical projection 32a formed on the top of the fixed ladder 30. Accordingly, the insulating contact blocks 19 and the fixed ladder are securely held in their respective positions by the stack plate 34 and are rigidly clamped to the horizontal leg of the L- shaped pole piece 12 by means of screws 39 and lock washers 40. For example, as shown in FIG. 3, the two elongated semi-circular grooves 20 of the intermediate insulating block 19 and the inner elongated semi-circular grooves 20 of the two outer insulating blocks 19 form a cylindrical opening for accommodating the passage of screws 39 which are screwed into the horizontal leg of the L-shaped pole piece 12. Further, it will be noted that the outer elongated semi-circular grooves 20 of the two outer insulating blocks 19 also provide a convenient method of holding the two coil leads 42 of the energizable coil 8. For example, a length of cambric spaghetti or insulating tubing if fixedly attached, such as by gluing, to semicylindrical surfaces of each of the grooves 20 of the outer insulating blocks 19 so that the coil leads 43 may be passed therethrough. This not only results in an orderly configuration but also prevents the coil leads from interfering with the normal operation of the relay, such as by restricting contact movement. The free end of each of the coil leads is provided with suitable connecting terminals 44, such as a solderless female tab socket, which is crimped onto the end thereof. The solderless terminals are, in turn, push-fit to the terminal po tions 45 which also are molded in the top of the insulating blocks 19. The terminal portions 45 in turn may be connected to a suitable source of power for energizing the coil 8.

The movable armature assembly 4 comprises an operating ladder or driver 50, an intermediate stop member 52 and an armature member 53 which is constructed of suitable magnetic material and has a rectangular cross section. Referring now to FIG. 2, a more detailed showing and a better understanding of the movable armature assembly can be obtained. The assembly is preferably of an integrally molded construction with the stop member 52 disposed intermediate the ends of the operating ladder 50 and the magnetic armature member 53 disposed at the lower end of the operating ladder 50. The assembly is suspended by means of the movable contacts 24 which have their free end passing through suitable slots or rectangular openings 51 appropriately located in the operating ladder 50. As shown in FIG. 1, the rear surface of the operating ladder 50 is disposed against the offset portions 25 of the movable contacts 24 while the front surface of the operating ladder 50 communicates with the punch tabs 26 which are shown bent upwardly for rigidly holding and detachably fastening the movable armature assembly 4 thereto. The armature member 53 has each side partially encompassed by enlarged molded shoulders 54 which are formed on the lower end of the operating ladder 50. Accordingly, the entire assembly 4 is held in guided alignment by the free ends of the movable contact springs 24 and the stop member is shown disposed adjacent the upper surface of the pole piece members 12 and 13 while the armature member 53 is disposed adjacent the under surface of the horizontal legs of the pole piece members 12 and 13. Therefore, with the relay deenergized the stop member 52 rests upon the upper surface of the pole piece members 12 and 13 thereby limiting the amount of downward movement and establishing the required magnetic air gap between each end of the armature member 53 and the under surfaces of the pole piece members 12 and 13. Preferably, a strip of self-adhesive insulating tape or a strip of non-ferrous metal is attached to the upper surface of each end of the armature member 53 for providing a residual air gap between the armature and the pole piece members. This insures that the armature member will not directly contact the pole piece members so that the residual magnetism will not cause the armature to stick to the pole pieces or fail to immediately release upon interruption of the coil current. In practice, the operating ladder and the integral stop member are preferably molded from suitable insulative material, such as clear polycarbonate, to allow readily visual inspection of the contact points. With the stop member constructed of suitable insulative material a soft effect is realized so that contact bounce is minimiz ed due to the deadening characteristics of the insulating material.

As previously mentioned, the presently described relay may be hand-wired or employed in a plug-in installation. For plug-in installations, a suitable molded mounting base 56, such as shown in chain lines in FIG. 1, is utilized in conjunction with the relay 1. A plurality of terminal connectors 56a, only one of which is illustrated in FIG. 1, cooperate with the terminal portions 22a, 23a and 24a of the front, back and movable contacts 22, 23 and 24, respectively. In order to facilitate the insertion and plugin connection of the relay with the mounting base 56, a pair of horizontal guides or indexing pins 57, one of which is shown in FIG. 1, communicate with suitable apertures 58 drilled into the lateral extending leg of pole piece member 12. It will be noted that the mounting base 56 is also provided with a shoulder 59 and a notch 60 at its upper extremity which cooperate with the rearward extending hook-like portion 36 of the stack plate 34. As shown in FIG. 1, the rearward extending portion 36 of the stack plate 34 is resilient biased downwardly so that the hook portion snaps into the notch 60 for securely holding and locking the mounting base 56 in relation to the relay. Preferably, the mounting base may be fastened by means of a conventional U-shaped mounting bracket which encompasses an elongated mounting bar having a rectangular cross section in a rack-type installation. As shown, the insulative mounting base 56 is provided with suitable bores 61 which are countersunk at the forward end for accommodating the screws and nuts common to the U-shaped bracket.

The relay may be readily detached and disconnected from the mounting base 56 by grasping handle 16 and applying a twisting pulling motion to unsnap the hooklike portion 36 from the notch 60.

In hand-wiring installations, it will be noted that the U-shaped mounting bracket may be directly fastened by appropriate screws threadedly engaging threaded apertures 62 provided in the lateral arm of the pole piece member 12. Accordingly, the relay is adapted for either plug-in or hand-wiring installations.

As previously mentioned, in its deenergized condition, the relay assumes a position as illustrated in FIG. 1 wherein the suspended armature 53 is in its released position. In this condition, the stop member 52 limits the amount of downward movement so that excessive stresses are not exerted on the contact springs. It will be noted that the stationary contact springs are permitted to move away from the shoulders 31 of the fixed ladder 30 during closure of the contact points so that a wiping action occurs, and therefore, the contact points are self-cleaning. With the relay deenergized and its magnetic armature released, the back contacts 23a of the various sets are closed by the heel contacts 24b while the front contacts 22b of the various contact sets are opened. Under this condition, the external circuits common to the back and heel contacts are completed while the external circuits common to the front and heel contacts are not completed.

Now when the relay becomes energized by appropriately connecting a source of power to the external circuit common to the coil connecting terminals 45, the magnetic flux created by current flowing through coil 8 causes the armature member 53 to be attrached upwardly toward the under surfaces of the pole piece members 12 and 13. The upward movement of the armature causes the operating ladder 50 to move therewith so that the movable spring contacts 24 are also displaced upwardly, as viewed in FIG. 1. The upward movement of this movable spring contact 24 causes the heel contacts 24b to initially break contact with the back contacts 23b and then to make contact with the front contacts 22b thereby interrupting the external circuits common to spring contacts 23 and 24 and establishing the external circuits common to the spring contacts 22 and 24. As previously mentioned, the strips of non-magnetic material 55 provided on the upper surface of armature member 53 prevents direct or intimate contact with the pole piece portions of the pole piece members 12 and 13 so that residual magnetism will not cause the armature 53 to stick upon the deenergization of the coil winding '8. When the current to terminals 45 is interrupted, the coil 8 becomes deenergized and the flux in the magnetic circuit rapidly decays so that the armature is immediately permitted to be released. The weight of the movable armature assembly or gravity is normally sufiicient to cause the assembly to move rapidly downward to a position where the stop member 52 again engages the upper surfaces of the pole piece members 12 and 13. However, where faster release of the relay is desired the movable contact springs may be biased or tensioned to urge the movable armature assembly downwardly thereby assisting the gravitational force. Accordingly, the relay again assumes its released position as shown in FIG. 1.

It will be appreciated that by employing a suspended type of armature assembly frictional wear and surface drag is eliminated between the moving and stationary parts. A suspended type armature also eliminates additional parts, such as, biasing springs, pivotal shafts or rods as well as fulcrum edges which were heretofore necessary elements in conventional pivoted armature types of relays.

In practicing the present invention, the movable contacts not only perform their switching transferring function but also operate to suspend and guide the armature with respect to the stationary structure. Accordingly, the multiple function of the movable contact springs not only eliminates the above-mentioned elements heretofore required but also results in a more economical relay construction since material and production costs for such elements have been completely omitted.

Further, the molded contact assembly herein described permits great versatility of the contact arrangement without the need of a plurality of insulating washers disposed between the contacts and also eliminates the tedious task of assembling the contact stacks as heretofore required. An entire contact set, namely, each of the insulating block and spring contacts, may be readily replaced with the minimum of time during maintenance and repair. Further, as previously mentioned various types of molded contact combinations, such as, single-pole-singlethrow or single-pole-double-throw and make-before-break or break-before-make, etc., may be readily conjointed during initial assembly.

.In addition, the stack plate not only retains the contact stacks and the fixed ladder in proper relationship with the relay proper but also is employed for holding and locking the relay to the mounting base when the relay is employed in a plug-in installation.

Likewise, the molded contact blocks 19 of the contact assembly not only function to rigidly maintain the contact springs in proper relationship to each other but also perform the dual function of accommodating the fastening screws 39 and of retaining the insulative tubings 42 for holding the coil lead 43 in nonobstructing relationship with the other parts of the relay.

Thus it is apparent that the new and improved relay of the present invention employs new and improved features which result in a more economical, durable and eflicient electromagnetic relay.

Further, while our invention has been described with reference to a preferred single embodiment thereof, it should be understood that numerous changes and variations may be made by those skilled in the art that will fall within the spirit and scope of our invention. Therefore, it is understood that the invention is not to be limited to the exact details described herein, but is to be accorded the full scope and protection of the appended claims.

Having thus described our invention, what we claim is:

1. An electromagnetic relay comprising an energizable coil, a core member extending through the center of said coil, a pair of pole pieces, one of said pole pieces being disposed at either end of said coil and engaging said core member, each of said pole pieces having a portion extending laterally from said core member to one side of said coil and having a pole face portion extending parallel to the axis of said coil, a contact assembly having a plurality of elongated stationary and movable contact springs fixedly secured to the parallel extending portion of one of said pole pieces so that the said contact springs are disposed parallel therewith, a fixed ladder disposed adjacent to the free ends of said contact springs for holding said stationary contact springs in proper relationship to said movable contact springs, a molded assembly including a movable ladder, an armature member and a stop member, said movable ladder suspended from the free ends of said movable contacts so that said armature member is disposed beneath and is attracted upwardly toward the undersurface of said pole face portions when ever said coil is energized and said stop member is disposed above and engages the upper surface of said pole face portions whenever said coil is deenergized.

2. An electromagnetic relay as defined in claim 1, wherein said contact assembly includes a plurality of individual contact stacks having separate molded insulating blocks which are disposed in side-by-side relationship on the parallel extending portion of said one pole piece.

3. An electromagnetic relay as defined in claim 2, wherein each of said insulating blocks includes a projection cooperating with an aperture provided in the parallel extending portion of said one pole piece for properly positioning said insulating blocks with respect to said one pole piece.

4. An electromagnetic relay as defined in claim 3, wherein a stack plate including a plurality of depending lugs cooperating with suitable recesses provided in said insulating blocks for maintaining said contact stacks in side-by-side disposition and including a forward extending portion cooperating with said fixed ladder for holding it rigidly against the parallel extending portion of said one pole piece.

5. An electromagnetic relay as defined in claim 1, wherein self-adhesive insulating tape is disposed on the upper surface of said armature member to provide a residual air gap between said armature member and said pole face portions when said coil is energized.

6. An electromagnetic relay as defined in claim 1, wherein said movable ladder includes a plurality of slots for accommodating the free ends of the said movable contact springs and said movable contact springs having an offset and a punched tab for holding said movable ladder in proper relationship thereto.

7. An electromagnetic relay as defined in claim 4, wherein said stationary and movable contact springs have terminal portions adapted for receiving wire connections and adapted for plug-in connection to a mounting base having guide pins cooperating with apertures in the lateral extending portion of said one pole piece and having a shoulder portion engaged by a hooked portion of said stack plate for latching the relay to said mounting base.

8. An electromagnetic relay as defined in claim 2, wherein an insulative spaghetti tubing is glued to semicylindrical recesses provided in said end insulating blocks for accommodating the electrical lead-in wires of said energizable coil.

9. An electromagnetic relay as defined in claim 7, wherein a handle is secured to said core member for easily removing the relay for said mounting base.

10. A relay comprising a magnetic core, an energizable coil surrounding said core, a pair of pole pieces, each pole piece secured to the respective ends of said core and extending upwardly and inwardly to within a given distance of each other, a contact assembly having a plurality of elongated stationary and movable contact springs molded in blocks of insulating material, a fixed ladder disposed adjacent the free ends of said contact springs, a stack plate having an intermediate portion engaging said blocks of insulating material and having a forward extending portion engaging said fixed ladder for holding said blocks and said fixed ladder to one of said pole pieces, a molded assembly having an operating ladder suspended from the free ends of said movable contact springs, having an armature secured to the lower end of said operating ladder and disposed below said pole pieces, and having a stop member secured intermediate said movable ladder and disposed above said pole pieces.

11. A relay as defined in claim 10, wherein each of said pole pieces is L-shaped.

12. A relay as defined in claim 10, wherein said contact assembly includes a plurality of blocks of insulative material disposed in side-by-side relationship on one of said pole pieces.

13. A relay as defined in claim 12, wherein each of said plurality of blocks of insulating material includes a projection which cooperates with a hole in said one pole piece for locating said blocks in proper relation thereto.

14. A relay as defined in claim 12, wherein each of said plurality of blocks of insulating material is provided with a semi-circular groove at each side thereof for accommodating fastening means which cooperate with said stack plate for holding said blocks and fixed ladder to one of said pole pieces.

15. A relay as defined in claim 14, wherein a length of insulative tubing is attached to a pair of said semicircular grooves for retaining the leads of said energizable coil in place.

16. A relay as defined in claim 10, wherein the free ends of said movable contact springs are provided with an offset and a punched tab for securely fastening said operating ladder to said movable contact spring.

17. A relay as defined in claim 10, wherein said fixed ladder includes a plurality of laterally projecting shoulders which cooperates with said stationary contact springs for holding said contact springs in their normal rest positions.

References Cited UNITED STATES PATENTS 2,640,895 6/1953 Boswau 335l25 2,833,885 5/1958 Wells 335192 2,903,520 9/1959 Frank 335129 3,418,608 12/1968 Angel 335131 BERNARD A. GILHEANY, Primary Examiner H. BROOME, Assistant Examiner US. 01. X.R 335-192, 

